Application slows when OpenMP switch is used

[sachini1]

Hi,

Whenever I add the -openmp switch to the compiler, even without using any openmp pragmas in the code, the application slows down. Does this happen with all applications? or is it something wrong with the settings and other switches in the compiler?

Would be happy if someone can help. Thanks in advance.

Sachini

[TimP]

Does applying the -auto switch (implied by -openmp) slow down your application? If so, do interprocedural optimizations help? You must know more about your application than you have told us.

[sachini1]

yes, interprocedural optimization speeds up the application. but when i add the /Qopenmp switch (even without any openmp pragmas in the code), the application slows down significantly.

thanks for you effort.

Sachini

[JenniferJ]

Could you report this to PremierSupport? itwould be great.

If not, please attach the IPO report with /Qopenmp, and the IPO report without /Qopenmp.

1. icl /Qipo /Qopenmp /Qopt-report_file ipo_rep_omp.txt /Qopt-report-phase ipo app.cpp

2. icl /Qipo /Qopt-report_file ipo_rep.txt /Qopt-report-phase ipo app.cpp

Thanks,

Jennifer